Couple o' points:

There are no "Mexican" AA lounges.

I've been regularly using the AA Flagship Lounges (First class lounge) as well as the Admirals Clubs, throughout the US. No problems as recently as Apr 30.

If lounge access disappears on June 1, then I suspect so will reciprocal upgrades, as the lounge access arrangement predates the upgrade arrangement. I'm particularly glad I've begun my AA Platinum Challenge. Six days, one trip, and an additional expenditure of CAD$114, and I'm there. But while that will guarantee me upgrade availability, it won't get me into a lounge.

But that same Challenge will most likely preclude me making Exec Plat on CP this year, notwithstanding that I may not have made it in anycase.

I've also been using the AA Executive Platinum Desk on a regular basis, without problem.